More about PAS

When I suggested cervix for a PAS control - I intended it for use as a
glycogen control. Kidney is the most sensitive control for the reaction - as
there are fewer reactive sites. I weakened reaction can be determined very
quickly. I think I said before on histonet that we stained a multitude of
kidney biopsies - and to be certain that the results were good - we used a
staining jar of reagent for two batches of slides only. Whoever poured the
reagent into the jar, could put it back in the refrigerator (and we always
refrigerated). If you got it from the refrigerator in the staining jar, then
you dumped it after use. We could always tell when someone tried to "cheat",
because the results showed a decrease in staining.
As Rande indicated, small intestine is a good control for mucin, but it is
not as sensitive for the quality of the reaction as kidney. And it goes
without saying that a section containing fungi should be used for the PAS
reaction on tissue suspected of containing fungi.
Several of the histochemists - Troyer, Vacca, and I think Lillie - state that
because the water supply in many cities is heavily chlorinated and will
reoxidize the Schiff reagent if you go directly into running water - it will
increase the possibility of false staining - so I think that the sulfite
rinse is probably a good idea.
Freida